A Diffuse-Interface Description of Electron Tunneling across Solid Electrolyte Interphases

Solid electrolyte interphase (SEI) is an electronically insulating layer on battery electrode due to electrolyte decomposition, which critically affects the battery performance. Electron tunneling is a key short-term electron transport mechanism that controls the SEI thickness and its growth behavior. The electron tunneling behavior is governed by the static Schrödinger equation and the tunneling barrier of SEIs, which shows an exponential decay of electron probability across the SEI layer. Here we develop a diffuse-interface description of electron tunneling behavior by formulating a phase-dependent tunneling barrier, so that the electrode/SEI and SEI/electrolyte interface positions do not need to be explicitly tracked when numerically solving the Schrödinger equation. We will show that this diffuse-interface description can accurately and efficiently predict the electron tunneling behaviors in 2D and 3D especially when the electrode/SEI and SEI/electrolyte interfaces are highly nonuniform. Furthermore, we will show that it can be seamlessly integrated with the phase-field simulation of electrodeposition and SEI growth in lithium-ion batteries, providing guidance for controlling the SEI morphology and improving the battery performance.